Purpose
The objective of this paper is to review the use of the fog index in accounting research.

Design/methodology/approach
This paper uses a systematic literature review (SLR) methodology with a sample of 126 accounting research articles. The review applies the theoretical framework of disclosure's stewardship, valuation and accountability roles to identify the contributions and challenges of using the fog index in accounting research.

Findings
This paper shows that the primary contribution of the fog index to accounting research relates to the disclosure obfuscation hypothesis (e.g. whether management obfuscates narratives associated with earnings). It also finds that the challenge in using the fog index is in disentangling its measure of firm environmental complexity from narrative obfuscation. Regarding disclosure utility, there is limited evidence on the differential effects of complexity on investor types and whether the fog index findings are associated with narrative obfuscation or firm environmental complexity is driven by investor types.

Research limitations/implications
The authors develop a research database of fog index studies categorised based on contributions to disclosure obfuscation or disclosure utility, highlighting contributions to the stewardship, valuation and accountability roles of disclosures, which researchers can use to develop future studies.

Originality/value
This paper contributes to accounting literature by offering the first comprehensive review on the use of the fog index in accounting research. It offers researchers a consolidated review of the study of linguistic complexity of accounting information and disclosure functions using a theoretical framework that can inform regulators, policymakers and future researchers in designing future research/policy.